Admittance to Detect Alteration in Cardiac Hemodynamics with an Implanted Commercial Right Ventricular AICD Leads

Introduction: Contemporary AICDs discriminate between SVT and VT based on intracardiac electrograms (EGM). Unfortunately, current discriminators do not allow differentiate between hemodynamically stable and unstable arrhythmias. Hypothesis: Using implanted commercial RV leads, we propose that the admittance method can be used to accurately track right ventricular (RV) hemodynamics. Changes in RV admittance measurements should parallel alteration in left ventricular (LV) stroke volume (SV). Methods: Dual chamber AICD leads were implanted in eight canines. One month after implant, rapid RV pacing was used to induce dilated cardiomyopathy. LVSV was obtained with trans-esophageal echocardiography (TEE). Complex tripolar admittance measurements were made between the RV ring and coil electrodes. The admittance method was used to separate myocardial and blood components, resulting in a signal proportional to RV blood volume (Fig 1A). To assess the capacity of admittance to track alterations in cardiac hemodynamics, using a single chamber RV lead, RV admittance measurements were compared to LVSV obtained by TEE during decremental atrial pacing (AOO). Results: The TEE acquired drop in LVSV with step-wise AOO pacing was closely tracked by instantaneous blood admittance (Fig 1B). The percentage change in admittance derived RVSV closely follows LVSV (r=0.7, Fig 1C). Conclusions: RVSV can be monitored using the admittance method with commercial RV AICD leads. Admittance derived changes in RVSV track alterations in TEE LVSV. Measurement of RV hemodynamics with single chamber commercial AICD leads coupled with EGMs could potentially provide devices with new information to discriminate between hemodynamic stable and unstable arrhythmias and reduce inappropriate AICD shocks.